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M_Den

Ha (or duo NB?) filter choice for modified DSLR?

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Hi all,

This is an amazingly helpful forum¬†- there's so much information on here (I'm new and have just found you, by the way...<waves vigerously! ūüėÉ>)...

I'm contemplating getting a modified dslr for imaging in narrowband  - and before I take the plunge, I could really use your help figuring out the best route for filter choices.

I'm eyeing up a second-hand, fully modified DSLR and a (idealy clip-in) filter of some kind.  I've seen good reviews for Cheap Astrophotography and have sent them an email, I'm quite tempted by their 600d camera.  I realise DSLRs aren't ideal for narrowband imaging, but do feel it's the only option I can afford at the moment.  Some will be through the telescope (a skywatcher ED80) and some potentially through camera lenses on the Star Adventurer.  I was planning to start out with simple Ha imaging.  I'd then think about SII or OIII filters further down the line...OR, I could invest now in a duo-narrowband filter, and get Ha and OIII for a similar(ish) price to buying the two filters individually (though not sure there is a clip-in duo narrowband, so not sure I'd be able to use it with camera lenses?)

So, which filter would you recommend?  Purely Ha or go for a Duo NB?  (Presumably Ha maps to red and OIII to blue?)

If I just focus on Ha, I gather 6nm is preferable to 12nm.  I could go Astronomik 12nm clip in, which gets good reviews, for about £180ish, but then First Light Optics have the 7nm Optolong for a few quid less than that...the problem is I've seen some posts on other forums about the quality assurance of the Optolongs (as well as the statement on Astronomik's website), and I'm not sure how much of that is bashing the new product on the block and how much is simply 'you'll get what you pay for'...the Astronomik 6nm clip-in is probably £100 more.....

Any views or experiences of any of the above (or recommendations for alternatives) would be gratefully received!

Thanks,

Mike

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I would go for the Duo as it is what I intend to do myself, the Optolong has the better band pass from what I am told as ZWO have now brought their own to the marketplace. There is nothing wrong with using a DSLR, I have done for two years and got some nice results. Some of the other members on here have really turned out some stunning images with DSLR's, making mine look poor.

Maybe someone else will advise on a single clip on filter though It is something that didn't try and know little about, I do like the advertising of these duo band filters though.

Alan

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I use a modified & cooled 450D. All the following really need at least twice as much data. You need to be quite brutal with the stretching, especially with Ha.

This is Baader 7nm Ha, just using the red channel:

Crescent.thumb.png.9d25390220faba7688bcb6490cc1b7d2.png

SH2-86.thumb.png.22f79d975f736a2d0eec90d8d2ce0ae9.png

CED-214.thumb.png.8cd67aa6f73176369c0d689c2244d606.png

These are my tests with the Optolong Triple band (it lets OII, Hb and Ha through), although it has two 'peaks'. The elongated stars are caused by accidental tilt.

Worked well on the veil, lots of OIII, shame about my targeting:

1486339540_VeilTest.thumb.png.48d77354bf594ed5f30512d64d0e863a.png

Heart didn't show much if any OIII with it:

245697781_hearttest.thumb.png.4d4dc0ca922d08a64d736dbfa70fdf5b.png

Fake hubble palette using the optolong:

165085859_pelinanpseudohubble.thumb.PNG.849b8cea4c43000a0c69975316e2ec44.PNG

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18 hours ago, alan potts said:

I would go for the Duo as it is what I intend to do myself, the Optolong has the better band pass from what I am told as ZWO have now brought their own to the marketplace. There is nothing wrong with using a DSLR, I have done for two years and got some nice results. Some of the other members on here have really turned out some stunning images with DSLR's, making mine look poor.

Maybe someone else will advise on a single clip on filter though It is something that didn't try and know little about, I do like the advertising of these duo band filters though.

Alan

Many thanks, Alan, that's great.  Yes I've seen some excellent looking photos / videos of the Duo and I'm quite intrigued...and very tempted!  I'm keen to get the right balance between spending too much and being in a position a few days / weeks after buying something of wishing I'd gone one step up, if that makes sense!  Haven't done narrowband before so wondering if I should learn the ropes in Ha first.  Was thinking I could always opt for the cheaper option and look to re-sell it if I don't get on with it, or want to take the next step....but then I think of the Veil and the Crab and the Rosette (not to mention all of Neil's targets in his post above) and I want all of the filters immediately!!!

Thanks again!

Mike

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18 hours ago, Stub Mandrel said:

I use a modified & cooled 450D. All the following really need at least twice as much data. You need to be quite brutal with the stretching, especially with Ha.

 

Thanks Neil - it's really helpful to see some examples like that.  I'd seen and heard good things about the Baader 7nm.  Some lovely images there - I do like that Crescent nebula - one of my favourite objects!  And your Veil made me smile - lovely image and the framing is still significantly better than I managed! 

Thanks again for the helpful examples...I've got some thinking to do!

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No problem, I think the lessons I've learned are:

DSLR narrowband isn't easy, you need (fairly) long exposures which generally means guiding.

Processing requires a fair bit of learning, and it's worth investing in good noise removal and contrast enhancing software, like Astra Image.

The dual band filter doesn't suppress stars as much as a Ha filter and gives them unnatural colours.

Most objects have much more Ha than OIII signal and I think a lot of data collection will be needed to get the OIII signal up out of the noise background.

With narrowband filters, Ha is feasible for DSLR, OIII is more challenging and SII is likely to be difficult.

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